Abstract: Genetic diversity among 6 populations of Ranalisma rostratum, Sagittaria guayanensis ssp. lap-pula, Sagittarw, wuyiensis and Sagittarui pygmaea were investigated by using the assay of vertical slab poly-acrylamide gel electrophoresis. Endangered species R. rostratum with inbreeding and great proportions of vegetative reproduction maintained lower level of genetic variation than the average of plant species. Its ex-pected heterozygosity and observed herozygosity were 0.064 and 0.104 respectively. S. guayanesis with in-breeding maintained very low level of genetic diversity. Its expected heterozygosity and observed heterozygos-ity were 0.039 and 0.066 respectively. The genetic diversity of S. pygmaea with great proportions of out-breeding and vegetative reproduction was the highest among these four species.

Key words: Allozyme, Genetic diversity, Ranalisma rostratum, Sagittaria guayanensis, Sagittaria wuyiensis, Sagittaria pygmaea